Premorbid functional reserve modulates the effect of rehabilitation in multiple sclerosis

Background Premorbid physically and intellectually enriching lifestyles have increasingly been recognized as able to mitigate the risk of disease-related disability in patients with multiple sclerosis (MS). Objective To explore if premorbid physical activity, cognitive reserve and trait personality act as proxies for functional reserve that contributes to rehabilitation outcome. Methods We recruited all patients previously enrolled in two pilot trials investigating the effect of home-based video game training in improving balance (Study 1) and attention (Study 2) for additional assessments with the Historical Leisure Activity Questionnaire (HLAQ; a proxy for premorbid physical activity), Cognitive Reserve Index Questionnaire (CRIQ), and Temperament and Character Inventory (TCI). Hierarchical logistic regression (HLR) analyses tested the association of HLAQ, CRIQ, and TCI with training effect on balance (static posturography) and on attention (Symbol Digit Modalities Test). Results We identified 94% (34/36) and 74% (26/35) of patients participating at the original Study 1 and Study 2, respectively. HLR analyses showed an exclusive "intra-modal" modulation of rehabilitation outcome by functional reserve, given that (1) larger training effect on balance was associated with higher HLAQ (OR = 2.03, p = 0.031); (2) larger training effect on attention was associated with higher CRIQ (OR = 1.27, p = 0.033). Furthermore, we found specific personality traits associated with (1) greater training effect on balance (self-directedness; OR = 1.40, p = 0.051) and lower training effect on attention (harm avoidance; OR = 0.66, p = 0.075). Conclusion We hypothesize that premorbid physical and intellectual activities not only act as a buffer for limiting the MS-related damage but also as functional reserve that can be retrieved by task-oriented training to promote recovery through rehabilitation.